1. Field
The present invention relates to distributed ignition (or heating) of fuels, propellants, energetic materials and related combustible materials, and in particular it relates to the use of certain ignition agents, in ignition of fuels, propellants, energetic materials, and related combustible materials.
2. Description of the Related Art
Many industrial processes that utilize chemical reactions in their applications often require an initiation stimulus to start the conversion of the chemicals. The process that initiates the combustion of fuels is commonly referred to as ignition. It is a critical systems component for most combustion processes especially in mobile or stationary power producing machines. For example, improper ignition during the firing of a rocket engine during lift-off can lead to a catastrophic engine failure and possible loss of the spacecraft and human life. Also, the ignition characteristics in a gasoline-fueled automotive engine can strongly affect the fuel's initial burn rate, the chamber's combustion efficiency and the exhaust stream's emission profile.
Although many ignition methods exist, by far the most popular one is the spark igniter. It requires high energy inputs via high voltage circuitry and often heavy components, and by its nature is a single-point stimulus method. In other words, the ignition initially occurs at the point where the igniter is located and it is hoped that the flame will spread from there throughout the volume in which combustion is desired.
Other ignition methods such as plasma jet injection or flame jet initiation, and high-power laser ignition are all bulky, heavy and expensive to operate. Yet other approaches to ignition can be through the usage of pyrolytic charges or via the mixing of hypergolic chemical components, or via activation over catalytic beds, all of which either make use of hazardous chemicals and/or of highly specialized materials or sophisticated mixing machinery. Again these are either single-point initiation methods as in the case of focused-laser ignition or limited to a narrowly defined region in the combustion chamber.
Another disadvantage of these ignition systems, with the exception of perhaps lasers, is that once they are installed on an engine, the ignition location remains fixed with respect to the combustion chamber. It is often preferable to have a plurality of ignition points to initiate a uniform or well-distributed combustion initiation. However, using the above described fixed point ignition techniques, multi-point ignition within a chamber can only be achieved by repeated implementation of the ignition hardware, which spatially can be very restrictive to attain as well as increasing engine size and mass over a single-point ignition system. Additionally, the ability to select and continuously vary the ignition locations or regions in an engine as a parameter, or “distributed ignition,” is a critical and useful engineering design component for better control of the start-up transient and for developing high efficiency combustion chambers. Current ignition methods also suffer from one or more other disadvantages such as combustion instability, start-up transients which decrease engine efficiency, and increased pollutant emissions.
Thus, an ignition method is needed which is effective as a multi-point or distributed ignition while allowing design versatility in decreasing mass and size of the engine. At the same time, such a method should exhibit increased ignition efficiency and reduced harmful emission content.